JP3132726B2 - Recycling method for expanded polystyrene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering and recycling expanded polystyrene, which is still used in large quantities as a packaging material for home appliances and AV equipment and as a molding material for food trays.

[0002]

2. Description of the Related Art Expanded polystyrene (so-called expanded polystyrene) is produced using styrene resin as a main raw material, and is extremely inexpensive, easy to mold, and excellent in shock absorbing properties. Products and AV
It is still used in large quantities as packing materials for equipment and the like, and molding materials for food trays.

However, foamed polystyrene has various problems in disposal. In other words, when landfilled, it is not decomposed in the soil and remains semi-permanently, and when incinerated, a large amount of heat is generated during incineration, and the incinerator may be damaged.

[0004] Therefore, recently, there has been an attempt to recover and recycle foamed polystyrene instead of discarding it, in part because environmental protection is regarded as important.

[0005]

As a technique for recovering and recycling expanded polystyrene, a method of pyrolyzing expanded polystyrene to use it as a fuel having a low molecular weight as a fuel and a method of melting expanded polystyrene by heat to block it are used. It has been known. However, all of these methods require large equipment and increase equipment costs, generate a strong odorous gas when melted by heat, adversely affect the environment and the human body, and produce products obtained as a result of recycling. However, it was difficult to say that it was suitable for practical use due to the deterioration of physical properties.

Moreover, since expanded polystyrene has a small specific gravity of about 0.02 and a large volume for its weight, a considerable storage space is required for its recovery, and it has not been sufficiently promoted because it is not worth the cost. .

Therefore, a method of dissolving expanded polystyrene in an organic solvent to reduce its volume has been studied.
However, the organic solvent proposed here has a low flash point and is flammable, and has a problem in safety.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for recovering and recycling expanded polystyrene which can efficiently and safely collect and recycle expanded polystyrene.

[0009]

In order to achieve the above object, a first method for recovering and recycling expanded polystyrene according to the present invention uses a polystyrene dissolving agent containing isopropyl bromide and / or normal propyl bromide as a main component. A method for recovering and recycling foamed polystyrene, wherein the foamed polystyrene dissolving agent and the foamed polystyrene are brought into contact with each other, and the foamed polystyrene is dissolved by the foamed polystyrene dissolving agent. The obtained polystyrene dissolved product is subjected to a heat treatment to evaporate a solvent component to take out polystyrene.

The second method for recovering and recycling expanded polystyrene according to the present invention is a method for recovering and recycling expanded polystyrene using a dissolving agent for expanded polystyrene containing isopropyl bromide and / or normal propyl bromide as a main component. Then, after contacting the foamed polystyrene dissolving agent with the foamed polystyrene and dissolving the foamed polystyrene in the foamed polystyrene dissolving agent while reducing the volume thereof, a solvent that weakens the dissolving power of the dissolving agent is added to the foamed polystyrene dissolving agent. The method is characterized in that polystyrene is precipitated from the foamed polystyrene dissolving agent by mixing and then the precipitated polystyrene is separated from the foamed polystyrene dissolving agent.

In the third method for recovering and recycling expanded polystyrene according to the present invention, the second solvent for weakening the dissolving power of the first solvent in the first solvent comprising isopropyl bromide and / or normal propyl bromide. A method for recovering and recycling expanded polystyrene using a polystyrene dissolving agent having a KB of more than 57 and less than 83 as a main component, which is made by mixing the above polystyrene solvent. Precipitating polystyrene from the foamed polystyrene dissolving agent while contacting the polystyrene and dissolving the foamed polystyrene in the foamed polystyrene dissolving agent while reducing the volume thereof,
Thereafter, the precipitated polystyrene is separated from the foamed polystyrene dissolving agent.

More preferably, the foamed polystyrene dissolving agent is at least one selected from the group consisting of nitroalkanes, ethers, epoxides and amines.
The one to which a stabilizer composed of a kind of compound is added is used.

Still more preferably, a foamed polystyrene solubilizer to which a fragrance is added is used.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for collecting and recycling expanded polystyrene according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the procedure of a first embodiment of a method for collecting and recycling expanded polystyrene according to the present invention. In this method, isopropyl bromide (alias: isopropyl bromide or 2-bromopropane, hereinafter referred to as IPB) and normal propyl bromide (alias: n-propyl bromide or 1-bromopropane,
(Hereinafter referred to as NPB) is contacted with a foamed polystyrene dissolving agent mainly comprising NPB) to dissolve the foamed polystyrene. IPB and NPB have been found as solvents capable of dissolving expanded polystyrene and shrinking the volume thereof as a result of intensive studies by the present inventors. IPB and NPB are safe and easy to handle solvents that have no flash point and have flame retardancy. The dissolving agent for expanded polystyrene containing IPB and / or NPB as a main component is brought into contact with expanded polystyrene by dipping or spraying. By this contact, the expanded polystyrene is immediately dissolved and its volume gradually shrinks. When the expanded polystyrene is dissolved in the dissolving agent, its properties change into a jelly or syrup. The dissolution rate and the volume shrinkage rate of the expanded polystyrene are high, and the process of dissolving the expanded polystyrene and reducing the volume can be performed smoothly.

FIG. 2 shows IPB for expanded polystyrene.
4 shows the dissolution performance of NPB and NPB. From this figure, it can be seen that by bringing the expanded polystyrene into contact with IPB and / or NPB, the expanded polystyrene can be dissolved and its volume can be considerably reduced. In this process, the expanded polystyrene may be completely dissolved in a large amount of the dissolving agent, or a small amount of the dissolving agent may be sprayed to simply reduce the volume.

The dissolving agent for expanded polystyrene includes IP
Both B and NPB may be blended, or only one of them may be blended alone. In addition, other solvents besides IPB and NPB may be mixed in the foamed polystyrene dissolving agent, as long as there is no problem in the dissolving ability of the foamed polystyrene. The foamed polystyrene to be dissolved in the present invention includes, for example, a foamed polystyrene molded article such as a used food tray or a packing material. These foamed polystyrene moldings may be directly dissolved as they are in their original shape, or may be crushed to form
After being made into a granular form or a powder form, it may be dissolved.

After completion of the dissolving treatment, the foamed polystyrene dissolved product obtained by dissolving the expanded polystyrene is subjected to a heat treatment. In this heat treatment, the solvent component contained in the dissolving agent is evaporated. By this heat treatment, the solvent component is removed, and the polystyrene remains. The remaining polystyrene can be reused again as expanded polystyrene, a polystyrene molded product, or a raw material of various other products including polystyrene. On the other hand, if the solvent component to be evaporated is recovered by distillation, it can be repeatedly reused as the main component of the foamed polystyrene dissolving agent or as a solvent that reduces the dissolving power.

According to this method, foamed polystyrene can be recovered or recycled by dissolving while reducing its volume, and a foamed polystyrene dissolving agent containing IPB and / or NPB having flame retardancy as a main component is used. Therefore, collection and recycling can be performed safely and easily. Moreover, the expanded polystyrene dissolved in the expanded polystyrene dissolving agent can be taken out by an easy method of heat treatment, and the solvent component evaporated by the heat treatment can be reused by collection, so that the collection and recycling can be performed efficiently and efficiently. Can be done economically.

In the above embodiment, if high-purity polystyrene cannot be obtained because impurities such as dirt, dust, and dust are mixed in the dissolving agent in which the expanded polystyrene is dissolved, after dissolving the expanded polystyrene, After adding a large amount of a solvent such as IPB and / or NPB to the dissolving agent in which the polystyrene is dissolved so as to have sufficient fluidity, a process of filtering to remove the impurities is added.

<< Second Embodiment >> FIG. 3 shows the procedure of a second embodiment of the method for collecting and recycling expanded polystyrene according to the present invention. In this method, a foamed polystyrene dissolving agent containing IPB and / or NPB as a main component is contacted with a foamed polystyrene by dipping or spraying to dissolve the foamed polystyrene while reducing its volume, and then dissolve the foamed polystyrene. A solvent that reduces the dissolving power is mixed with the dissolving agent. If a solvent that lowers the dissolving power is mixed, the dissolving power of the dissolving agent is weakened, and the polystyrene in the dissolving agent cannot be completely dissolved in the solvent and precipitates outside.

Here, the solvent which lowers the dissolving power of the dissolving agent has a lower dissolving power than IPB and NPB which are the main components of the dissolving agent, that is, a KB value (kauributanol value: also called a kauributanol value). But less than 125 solvents are used which are smaller than IPB and NPB. As the solvent, for example, propylene carbonate (PC), dialkyl carbonate (M2), dibasic acid ester or the like is used. In addition, alcohol solvents such as saturated or unsaturated alcohols having 1 to 10 carbon atoms, or hydrocarbon solvents such as n-heptane, isohexane, n-hexane and cyclohexane may be used. Further, esters such as isopropyl acetate, butyl acetate, methyl lactate, ethyl lactate and butyl lactate, ethers such as butyl phenyl ether, tetrahydrofurale and furfural, or heterocyclic compounds may be used. Two or more of these solvents may be mixed with the dissolving agent or one of them may be mixed alone. Here, it is preferable to use propylene carbonate which has a high deposition rate, a high flash point and excellent safety. The KB value (kauributanol value) is an index for evaluating the solvent's dissolving power measured by the following method. That is, when the test substance was dropped into 20 g of kauributanol solution at 25 ° C., the volume (ml) of the test substance required until the solution became cloudy was represented.

FIG. 4 shows the relationship between the amount of propylene carbonate mixed and the amount of polystyrene precipitated.
Here, 40 g of expanded polystyrene was dissolved in 100 g of an expanded polystyrene dissolving agent containing NPB as a main component. From this figure, as the amount of propylene carbonate mixed with the expanded polystyrene dissolving agent increases,
It can be seen that polystyrene gradually precipitates from the dissolving agent.

In this embodiment, the precipitated polystyrene is separated from the dissolving agent by filtration, centrifugation, or any other appropriate separation method. The polystyrene taken out by this separation can be reused again as expanded polystyrene, a molded product of polystyrene, or a raw material of various products including polystyrene. Further, the liquid remaining after the separation of the polystyrene is subjected to IP by distillation and the like.
The solvent is separated into B and / or NPB solvent and a solvent that reduces their dissolving power. The solvent obtained by the separation and the solvent that reduces the dissolving power can be reused as the main component of the foamed polystyrene dissolving agent, a solvent that reduces the dissolving power, and the like.

According to this method, IPB having flame retardancy
In addition to using a polystyrene dissolving agent containing NPB as a main component, the polystyrene can be taken out without using heat treatment, and the collection and recycling of the expanded polystyrene can be performed safely and easily. In the foamed polystyrene dissolving agent used here, after separating polystyrene, IPB and / or N
PB and the solvent mixed later to reduce the dissolving power of the dissolving agent can be separated and reused.
Recycling can be performed efficiently and economically.

Third Embodiment FIG. 5 shows a processing procedure of a third embodiment of the method for collecting and recycling expanded polystyrene according to the present invention. In this method, as a foaming polystyrene dissolving agent, a KB solvent value obtained by mixing a first solvent composed of IPB and / or NPB with a second solvent that reduces the dissolving power of the first solvent exceeds 57. And 83
Use a polystyrene dissolving agent containing a mixed solvent less than the main component as the main component. The present inventors considered that IPB and / or NPB could be combined with the expanded polystyrene dissolving performance of IPB and NPB.
It has been found that when a mixed solvent prepared by mixing a solvent composed of B with a solvent that lowers the dissolving power thereof comes into contact with expanded polystyrene, the polystyrene precipitates together with the dissolution of the expanded polystyrene. As the solvent for reducing the dissolving power, propylene carbonate (PC) or another solvent described above is used. The solvent described above may be IPB and / or N
Two or more kinds or one kind is mixed alone with the solvent composed of PB. Among them, it is particularly preferable to use propylene carbonate which has a high deposition rate, a high flash point and excellent safety. Table 1 shows the results obtained by examining the mixing ratio of the mixed solvent of NPB and propylene carbonate (PC) and the KB value, and the dissolution of expanded polystyrene and the presence or absence of polystyrene precipitation.

[0027]

[Table 1] From Table 1, it can be seen that in the mixed solvent having a KB value of more than 57 and less than 83, dissolution of expanded polystyrene and precipitation of polystyrene occur simultaneously. In particular, NP
When the mixing ratio of B and PC was 1: 1, the dissolution rate was high and the amount of precipitation was large, which was preferable.

After the dissolution and precipitation treatment, the precipitated polystyrene is separated from the foamed polystyrene dissolving agent. Polystyrene taken out by separation, as in the previous example,
It can be reused again as a raw material for expanded polystyrene or molded products of polystyrene and other various products containing polystyrene. On the other hand, unlike the case of the first embodiment, the liquid remaining after the separation of polystyrene can be reused without separation by distillation or the like. That is, in this embodiment, since the solvent of IPB and / or NPB and the solvent for lowering the dissolving power of polystyrene are mixed and used from the beginning, the solvent for the expanded polystyrene of this embodiment is reused as it is. Can be planned. When the solvent for IPB and / or NPB or the solvent for lowering its dissolving power is insufficient at the time of reuse, the solvent is replenished to the solvent.

As described above, according to this method, the expanded polystyrene is dissolved and its volume is shrunk to recover or recycle the foamed polystyrene. In addition, the foamed polystyrene dissolving agent used here is separated as it is after the separated polystyrene is separated. It can be used, and the collection and recycling of expanded polystyrene can be performed extremely efficiently and economically.

When the solvent for reducing the dissolving power is a flammable material, the amount of the solvent is set as small as possible to make the flammable material less flammable. Is preferred.

Further, it is preferable that the specific gravity of the foamed polystyrene dissolving agent be adjusted to 1.0 or more by adjusting the mixing ratio of the solvent of IPB and / or NPB and the solvent for decreasing the dissolving power. In the case of a foamed polystyrene dissolving agent having a specific gravity of 1.0 or more, the precipitated polystyrene can be floated in the vicinity of the surface of the solvent and can be easily separated.

<< Other Embodiments >> IPB and NPB are:
Because it easily reacts with metals, especially aluminum and its alloys,
In order to prevent this reaction, it is preferable to add a stabilizer composed of at least one compound selected from nitroalkanes, ethers, epoxides and amines to the foamed polystyrene dissolving agent. If this stabilizer is added, the dissolution agent can be prevented from being deteriorated during storage, transportation, use (during collection or recycling), and the like.

The compound selected from nitroalkanes as the stabilizer includes nitromethane, nitroethane, 1-nitropropane, 2-nitropropane, nitrobenzene and the like. Compounds selected from ethers as stabilizers include 1,2-dimethoxyethane, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, trioxane, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, acetal, and acetone. Dimethyl acetal, γ-butyrolactone, methyl tert-butyl ether,
Examples include tetrahydrofuran and N-methylpyrrole. Compounds selected from epoxides as stabilizers include epichlorohydrin, propylene oxide, butylene oxide, cyclohexene oxide, glycidyl methyl ether, glycidyl methacrylate, pentene oxide, cyclopentene oxide, cyclohexene oxide, and the like. Compounds selected from amines as stabilizers include hexylamine, octylamine, 2-ethylhexylamine, dodecylamine, ethylbutylamine, hexylmethylamine, butyloctylamine, dibutylamine, octadecylmethylamine, triethylamine, and tributylamine. , Diethyloctylamine, tetradecyldimethylamine,
Diisobutylamine, diisopropylamine, pentylamine, N-methylmorpholine, isopropylamine,
Cyclohexylamine, butylamine, isobutylamine, dipropylamine, 2,2,2,6-tetramethylpiperidine, N, N-diallyl-P-phenylenediamine, diallylamine, aniline, ethylenediamine, propylenediamine, diethylenetriamine, tetraethylenepentamine , Benzylamine, dibenzylamine,
Examples include diphenylamine and diethylhydroxyamine.

Since an odor is generated from the foamed polystyrene dissolving agent composed of IPB and / or NPB, it is preferable to add a fragrance to the dissolving agent to cover the odor. As the fragrance used herein, for example, amyl acetate, isoamyl salicylate, borneol,
Examples include synthetic fragrances made of I-carvone, cinnamic alcohol, phenylethyl alcohol, and alpinia, and natural fragrances made of, for example, moon peach extract. In addition, as a fragrance, a strong organic solvent such as limonene, isoamyl acetate, benzyl propionate,
Ethyl butyrate, octyl alcohol or cyclohexanone may be used.

The present invention is generally carried out by dissolving expanded polystyrene in a dissolving agent at room temperature, but the dissolving temperature is not limited at all as long as the present invention is practicable.

[0036]

According to the first method for recovering and recycling expanded polystyrene according to the present invention, as described in the embodiment of the present invention, the volume of expanded polystyrene can be reduced or recovered or recycled, and the flame retardant can be obtained. Since the foamed polystyrene dissolving agent containing IPB and / or NPB having a property as a main component is used, collection and recycling can be performed safely and easily. In addition, foamed polystyrene dissolved with a foamed polystyrene dissolving agent can be taken out as polystyrene by an easy method called heat treatment,
Since the solvent component evaporated by the heat treatment can be reused by collection, the collection and recycling can be performed efficiently and economically.

Further, according to the second method for recovering and recycling expanded polystyrene according to the present invention, a flame-retardant IP
Since a foamed polystyrene dissolving agent containing B and / or NPB as a main component is used, the volume of the foamed polystyrene can be reduced and recovered or recycled safely and easily. After the polystyrene is separated, it can be reused, so that recovery and recycling can be performed economically and efficiently.

Further, according to the third method for recovering and recycling expanded polystyrene according to the present invention, the volume of expanded polystyrene can be reduced to recover or recycle, and the dissolving agent for expanded polystyrene can be distilled after polystyrene is separated. It can be reused without performing processing or the like, and collection and recycling can be performed more efficiently and economically.

[Brief description of the drawings]

FIG. 1 is a process flow chart showing a procedure of a first embodiment of a method for collecting and recycling expanded polystyrene according to the present invention.

FIG. 2 is a graph showing the dissolution characteristics of expanded polystyrene in IPB or NPB.

FIG. 3 is a process flow chart showing a procedure of a second embodiment of a method for collecting and recycling expanded polystyrene according to the present invention.

FIG. 4 is a graph showing the relationship between the amount of propylene carbonate mixed in the polystyrene dissolving agent according to the present invention and the amount of polystyrene precipitated.

FIG. 5 is a process flowchart showing a procedure of a third embodiment of the method for collecting and recycling expanded polystyrene according to the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yu Takanashi 626-5 Toriyamacho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture 105 Shin-Yokohama Court 105 (72) Inventor Yuji Onozuka 25-1 Shinohara-Nishimachi, Kohoku-ku, Yokohama-shi, Kanagawa (72) Inventor Minata Kaneko 5-26-3, Senmadainishi, Koshigaya-shi, Saitama (56) References JP-A-6-32938 (JP, A) JP-A-8-333473 (JP, A) JP-A-6 -298992 (JP, A) JP-A-59-221341 (JP, A) JP-A-60-161440 (JP, A) JP-A-7-179651 (JP, A) (58) Fields investigated (Int. . ^7, DB name) C08J 11/08 C08F 12/08

Claims (5)

(57) [Claims] 1. A method for recovering and recycling polystyrene foam using a polystyrene dissolving agent containing isopropyl bromide and / or normal propyl bromide as a main component. After performing a process of shrinking the volume of the expanded polystyrene while dissolving it with a dissolving agent, the foamed polystyrene dissolved product obtained by this process is heated to evaporate the solvent component to take out the polystyrene. To collect and recycle expanded polystyrene. 2. A method for recovering and recycling expanded polystyrene using a polystyrene dissolving agent containing isopropyl bromide and / or normal propyl bromide as a main component. After dissolving the expanded polystyrene in the dissolving agent while shrinking its volume, the expanded polystyrene dissolving agent is mixed with a solvent that weakens the dissolving power of the dissolving agent to precipitate polystyrene from the expanded polystyrene dissolving agent. A method for recovering and recycling expanded polystyrene, comprising separating precipitated polystyrene from the polystyrene dissolving agent. 3. The first solvent comprising isopropyl bromide and / or normal propyl bromide.
A method for recovering and recycling polystyrene using a polystyrene dissolving agent having a KB value of greater than 57 and less than 83 as a main component and prepared by mixing a second solvent that reduces the dissolving power of the solvent. A polystyrene was precipitated from the foamed polystyrene dissolving agent while the foamed polystyrene dissolving agent was brought into contact with the foamed polystyrene dissolving agent while shrinking the volume of the foamed polystyrene while dissolving the polystyrene in the foamed polystyrene dissolving agent. A method for collecting and recycling expanded polystyrene, comprising separating polystyrene from the dissolving agent for expanded polystyrene. 4. A foamed polystyrene dissolving agent to which a stabilizer comprising at least one compound selected from the group consisting of nitroalkanes, ethers, epoxides and amines is added. The method for recovering and recycling expanded polystyrene according to claim 1. 5. The foamed polystyrene dissolving agent to which a fragrance is added is used.
5. The method for collecting and recycling foamed polystyrene according to any one of items 1 to 4.